docs: clarify custom tools can execute scripts in any language with Python example

packages/web/src/content/docs/custom-tools.mdx

@@ -9,7 +9,7 @@ Custom tools are functions you create that the LLM can call during conversations
 
 ## Creating a tool
 
-Tools are defined as **TypeScript** or **JavaScript** files.
+Tools are defined as **TypeScript** or **JavaScript** files. However, the tool definition can invoke scripts written in **any language** — TypeScript or JavaScript is only used for the tool definition itself.
 
 ---
 
@@ -45,56 +45,7 @@ The **filename** becomes the **tool name**. The above creates a `database` tool.
 
 ---
 
-### Arguments
-
-You can use `tool.schema`, which is just [Zod](https://zod.dev), to define argument types.
-
-```ts "tool.schema"
-args: {
-  query: tool.schema.string().describe("SQL query to execute")
-}
-```
-
-You can also import [Zod](https://zod.dev) directly and return a plain object:
-
-```ts {6}
-import { z } from "zod"
-
-export default {
-  description: "Tool description",
-  args: {
-    param: z.string().describe("Parameter description"),
-  },
-  async execute(args, context) {
-    // Tool implementation
-    return "result"
-  },
-}
-```
-
----
-
-## Context
-
-Tools receive context about the current session:
-
-```ts title=".opencode/tool/project.ts" {8}
-import { tool } from "@opencode-ai/plugin"
-
-export default tool({
-  description: "Get project information",
-  args: {},
-  async execute(args, context) {
-    // Access context information
-    const { agent, sessionID, messageID } = context
-    return `Agent: ${agent}, Session: ${sessionID}, Message: ${messageID}`
-  },
-})
-```
-
----
-
-## Multiple tools per file
+#### Multiple tools per file
 
 You can also export multiple tools from a single file. Each export becomes **a separate tool** with the name **`<filename>_<exportname>`**:
 
@@ -125,3 +76,90 @@ export const multiply = tool({
 ```
 
 This creates two tools: `math_add` and `math_multiply`.
+
+---
+
+### Arguments
+
+You can use `tool.schema`, which is just [Zod](https://zod.dev), to define argument types.
+
+```ts "tool.schema"
+args: {
+  query: tool.schema.string().describe("SQL query to execute")
+}
+```
+
+You can also import [Zod](https://zod.dev) directly and return a plain object:
+
+```ts {6}
+import { z } from "zod"
+
+export default {
+  description: "Tool description",
+  args: {
+    param: z.string().describe("Parameter description"),
+  },
+  async execute(args, context) {
+    // Tool implementation
+    return "result"
+  },
+}
+```
+
+---
+
+### Context
+
+Tools receive context about the current session:
+
+```ts title=".opencode/tool/project.ts" {8}
+import { tool } from "@opencode-ai/plugin"
+
+export default tool({
+  description: "Get project information",
+  args: {},
+  async execute(args, context) {
+    // Access context information
+    const { agent, sessionID, messageID } = context
+    return `Agent: ${agent}, Session: ${sessionID}, Message: ${messageID}`
+  },
+})
+```
+
+---
+
+## Examples
+
+### Write a tool in Python
+
+You can write your tools in any language you want. Here's an example that adds two numbers using Python.
+
+First, create the tool as a Python script:
+
+```python title=".opencode/tool/add.py"
+import sys
+
+a = int(sys.argv[1])
+b = int(sys.argv[2])
+print(a + b)
+```
+
+Then create the tool definition that invokes it:
+
+```ts title=".opencode/tool/python-add.ts" {10}
+import { tool } from "@opencode-ai/plugin"
+
+export default tool({
+  description: "Add two numbers using Python",
+  args: {
+    a: tool.schema.number().describe("First number"),
+    b: tool.schema.number().describe("Second number"),
+  },
+  async execute(args) {
+    const result = await Bun.$`python3 .opencode/tool/add.py ${args.a} ${args.b}`.text()
+    return result.trim()
+  },
+})
+```
+
+Here we are using the [`Bun.$`](https://bun.com/docs/runtime/shell) utility to run the Python script.